This invention relates to a device for controlling advance and return movements of an original table of an electrostatic copying apparatus and, more particularly, to such a device provided with a mechanism for causing return movement of the original tube by a spring force.
It has hitherto been proposed to provide a mechanism for controlling the advance and return movements of the original table in which a spring is connected at its one end to the movable original table and at the other end to a frame of a copying apparatus, the original table being scanned by suitable driving means, and when the original table contacts with a limit switch provided at the end of the scanning stroke, the original table is disengaged from the driving means to return to the initial position under the action of said spring.
In such a mechanism, however, there are disadvantages that the speed of the return movement of the original table only depends upon the rate of the spring itself such that the spring rate must be increased and thus vibration of the original table may be caused when it abuts against a stop provided at the initial position and a relatively long waiting time is required to initiate a subsequent scanning stroke of the original table, and that as the time lapses the rate of the spring is decreased to vary the position at which the original table is stopped at the end of its return movement.